1. Technical Field
The present invention pertains to elevators, and, more particularly, to the field of elevator safeties.
2. Description of the Related Art
Existing elevator safeties are wedge action devices, which work in only one direction. Such a safety cannot guard against unintended travel of an elevator cab in both the up and down direction. To guard against unintended motion in the up direction by an elevator using a wedge action safety, the conventional solution is to install a counterweight safety with its own wedge action safety, thus adding significant cost and complexity to the elevator design. Besides the counterweight safety approach, there are other solutions to the problem of unintended cab motion in the up direction, such as rope gripping devices, and Bode brakes. However, all existing solutions to the problem of guarding against unintended motion in the up direction require a system in addition to the system that safeguards the elevator against unintended down motion.
One reason an existing solution requires an add-on system, is that until recently, elevator governors have been unidirectional. The present invention is a response to the development of a bidirectional elevator governor, which suggests the possibility of a bidirectional safety, rather than two different safeties, one for unintended motion in each direction.